The invention relates to a metal-clad installation, especially for a high tension metal-clad substation, comprising a conductor placed inside a metallic housing containing an insulating gas and formed at least by one section connected to an adjacent section by a pair of connecting flanges with tightening bolts between which is interposed the external border of a supporting insulator of said conductor. The supporting insulator divides said housing into tight compartments.
In a metal-clad installation of the mentioned type, a fault of tightness for example can be limited at a given compartment, with the remaining part of the installation not being affected. The presence of connecting flanges permits a dismantling of the installation and an inspection or repair of some parts of the installation. When the flanges are dismantled, the tightness near the joint is broken and the two adjacent compartments obligatorily come into contact with the atmosphere. Before returning into service, the two compartments must be cleaned and filled with insulating gas even if the intervention is limited to one of the compartments. An increase in work and a complication of the inspection or repair operation result from this.
An object of the present invention is to remedy to this disadvantage and to permit the draining and dismantling of one of the installation compartments while maintaining the adjacent compartments in a tight condition under the normal working pressure.
According to the present invention the installation is characterized in that near the tightening bolts and in the interface between one of the flanges and the external border there is provided a slot. The slot is capable of receiving, after removing the bolt, a small plate nut in which a screw to fix the border to the other of the flanges can be screwed.
During a dismantling, a first connecting bolt is removed and a small plate nut receiving a screw to fix the opposite flange is slid in the corresponding slot on the side of the flange having to be dismantled. This secures the external border of the insulator to the non-dismantled flange of the section. Each bolt is successively replaced analogously by the just mentioned screw and small plate nut, the dismantling being, of course, carried out symmetrically to prevent excessive stresses on the insulator. After replacing all the bolts, the insulator is rigidly secured to the flange of the unaffected section and without any tightness break of this section. The fastening is sufficiently solid to withstand the differential pressure being exerted on the insulator when the defective section comes into contact with the atmosphere.
It is advantageous to provide slots on the two interfaces of the flange pair to permit a fastening of the insulator to any of the flanges and thereby a dismantling of any of the connecting sections. The slots can be provided in the insulator border when casting this border. Or, according to a variant of the invention, the slots can be machine-finished in the contact faces of the flanges.
The shape of the slots and small plate nuts is advantageously half crescent-shaped surrounding the bolt, so as to distribute the tightening forces and to limit the stresses exerted on the insulator border. The surface affected by the slots is only a fraction of the surface of the insulator border in contact with the flanges, so as to prevent any distortion of the insulator and to guarantee the tightness holding.
It is advantageous to provide a slot near each bolt, but the number of slots can be limited if the strength of fastening and the stresses imposed to the insulator are low.